For sophomores and juniors interested in medical
school and undergraduate opportunities:
• A visit by Dr. Paul Catalana, Al Squire, and other guests from
Greenville Hospital System University Medical Center.
• In RMSC 122 (The Pit) starting at 6:30pm, Tuesday Oct 30th.
• Presentation and discussion on the new medical school at Greenville and
undergraduate opportunities through their MedEx program, including
clinical experiences and preparation for medical school.
1QQ # 21 for 10:30
Write each letter, and circle each correct response.
a) Small motor units typically consist of Type II B
myofibers.
b) A motor unit will have at least two of the three types
of skeletal myofibers.
c) Sphincters are classified as tonically contractile.
d) Muscle contraction in multi-unit smooth muscle is
synchronized by gap junctions.
e) Smooth muscles can contract even without a change
in membrane potential.
1QQ # 22 for 11:30
Write each letter, and circle each correct response.
a) Small motor units typically consist of Type II A
myofibers.
b) Large motor units generate greater tension than
small motor units and are recruited first.
c) Sphincters are classified as phasically contractile.
d) Muscle contraction in singleunit smooth muscle is
synchronized by gap junctions.
e) Cardiac myofibers have action potentials and twitch
durations that last about 1-2 milliseconds.
S1
29 October 2012
Chapter 10:
Control of somatic
motor systems
Riding a bike, playing piano,
swinging a bat or golf club….
Video of Trampoline Championship
Benjamin Zander: Classical Music and Shining Eyes
Eric Mongrain playing Air Tap
S2
Fig. 10.10a
Each region has
a homunculus
S3
Fig. 10.02
Formerly called “basal ganglia”,
consist of caudate, putamen, and
globus pallidus
Decision to move
S4
Fig. 10.01
Initiates motor command
Coordinates
secondary movements
Corticospinal and
corticobulbar
tracts
Balance and
complex
learned
movements
Pathways?
Other inputs:
Vestibular &
Visual!
Reflex
Examples of
motor
disorders:
Huntington’s
Disease and
Cerebellar
Disorder
S5
Jack Nicholson
One Flew Over the Cuckoo’s Nest
Frontal lobotomy
S 16
Pyramidal tract
Fig. 10.12
Corticospinal tract
Corticobulbar tract
Fine motor control, esp. of extremeties
Extra-Pyramidal tracts
Reticulospinal tract
Vestibulospinal tract
Originate in brainstem,
more involved with posture and equilibrium
Not monosynaptic!
Descending Pathways
S 17
Who Cares?
Video of Huntington’s Chorea
Video of Cerebellar Dysfunction
Video of Trampoline Championship
Locked-in Syndrome
S6
Local control
• Muscle spindle
Spindle
Afferent
gamma motoneurons
– Stretch receptor
– Intrafusal muscle fiber
• What is their role?
• The stretch reflex…
– Follow the reflex arc
– Be able to differentiate
function of afferent fibers,
alpha motor neurons, and
gamma motor neurons
Motor units of
alpha motoneurons
S7
Fig. 10.05ab
This doesn’t happen!
S8
Fig. 10.05c
Co-activation of alpha and gamma
motoneurons insures that the
stretch of muscle can be detected
regardless of the initial length or
state of contraction of that muscle.
S9
Fig. 10.06
Proprioception
pathway via dorsal
column-medial
lemniscus pathway
One component
of Stretch reflex is
monosynaptic
Most common
example:
patellar reflex =
“knee jerk reflex”
Synergistic
&
Antagonistic
S 10
Stretch Reflex
Monosynpatic excitation of motoneurons of
that muscle and synergistic muscles
and polysynaptic inhibition of motoneurons
to antagonistic muscles.
Recall frog reflex lab and existence of spinal
reflexes in single-pithed frogs.
Also, example Christopher Reeve and
patellar reflex.
S 11
Fig. 10.07
S 12
Golgi tendon organs
involved in a reflex to
oppose excessive
muscle tension.
Not monosynaptic.
Not shown:
ascending axons in dorsal
column-medial lemniscus tract.
S 13
Joint angle detectors and cutaneous mechanoreceptors
contribute to sense of body position (proproiception.)
Plus vision and vestibular inputs!
S 14
Crossed-extensor reflex: Common sense… check the book!
S 18
Lifting a load
and contraction velocity